1. Procedural Animation Lecture 8: Particle systems
Procedural Methods in 3D Computer Animation
Dr. Midori Kitagawa

2. Particle systems
Technique for modeling and animating a class of fuzzy objects, such as fire, clouds, and water.
Particle systems model such objects as clouds of particles.

3. Particle systems Over a period of time, particles are:
generated into the system
moved and changed within the system
removed from the system

4. Particle systems
No well-defined surfaces
Non-rigid objects
Dynamic

5. Particle systems Early examples:
"Genesis Effect from Star Trek II: The Wrath of Khan"
Particle Dreams" by Karl Sims.

6. Particle attributes Each particle has attributes such as:
Initial conditions
Initial position -- often supplied by a source geometry, e.g., a point, curve, surface, or volume
initial velocity and its variance
initial color, transparency, size, shape, and their variances,
Life expectancy and its variance
Current position, velocity, color, age, etc.

7. Per particle/frame
In each frame, the position of each particle is computed and updated using:
position and velocity of the particle in previous frame
acceleration of the particle
external forces, e.g., gravity, winds, attractors, drag
inter-particle forces
collision detection if there are geometries with which particles may collide.

8. Per particle/frame
Other attributes (e.g., velocity, age, and color) of each particle are updated for each frame
When the particle lives larger than its life expectancy, it's killed.

9. State dependent
For each frame, the system checks the current state of each particle and updates it for the current frame.
The state at the new frame depends on what happened in the past.
Can update itself properly only in a forward direction.
State dependent
Genesis Effect from Star Trek II: The Wrath of Khan"